Many military and commercial applications of satellite communication (SATCOM) and radar systems require rapid electronic beam scanning, often on the order of tens of microseconds or less, as well as continuous connectivity of communications for on-the-move vehicles. In a military scenario, it is crucial to maintain near total situational awareness. For example, a battle brigade needs reliable satellite communications in a moving platform environment. Maintaining connectivity is critical to advanced systems such as the Future Combat Systems (FCS) communication and data link system. In an FCS system, for example, it is desirable to simultaneously maintain concurrent surface-to-surface, surface-to-air, and surface-to satellite modes of operation. Radical vehicular platform movement, e.g., high performance fighter aircraft “dog fighting” maneuvers, further complicates the need for rapid beam scanning. The requirements of millimeter wave radar systems include imaging, target missile and armament seeking and guidance and fire control. Millimeter wave systems are also becoming increasingly important for commercial broadband connectivity SATCOM systems, including wireless Internet, Direct Broadcast System (DBS) satellite television systems and others. In addition, data link functions are required for current and next generation advanced military systems.
Phased array antennas offer significant system level performance enhancements for both military and commercial applications of advanced communications, data link, radar and SATCOM systems. A phased array antenna is a beam focusing antenna in which the relative phases of the respective signals feeding the antennas are varied such that the effective radiation pattern of the phased array is reinforced in a desired direction and suppressed in undesired directions. The relative amplitudes of constructive and deconstructive interference effects among the signals radiated by the individual elements determine the effective radiation pattern of the phased array. Phased array antennas provide rapid electronic radiation beam scanning as required by the various systems discussed above. The ability to rapidly scan the radiation pattern of a phased array antenna may allow for multifunction/multi-beam/multi-target, LPI/LPD (low probability of intercept and low probability of detection) and A/J (anti-jam) capabilities. Polarization matched satellite tracking and broad band, multi-function phased array architectures may also enable simultaneous reception of satellite TV and other data links.
Despite the benefits of phased array antennas described above, phased array antennas are often only integrated into the most sophisticated and expensive military and commercial applications due to prohibitively high costs. Traditional passive phased array antennas require tight mechanical tolerances, low loss RF feed manifolds, and an extremely high control and bias interconnect count. A phase shifter may be included in a radiating element to provide the required variation in electrical phase for the radiating element. A phased array antenna may include tens of thousands of radiation elements, phase shifters, etc. Accordingly, a large number of control lines may be required to provide the proper control signals, bias and chassis ground for the radiation element, phase shifters, etc. of a phased array antenna. In addition, separate electrical connections are typically provided for each radiating element and phase shifter to connect to signal sources (e.g., to receive RF signals and bias/control signals, respectively). For example, a typical 5-bit digital phase shifter requires positive and negative bias voltages, chassis ground, and five control lines, for a total conductor count of 8 lines for each element of a phased array antenna system. In this example, a 10,000 element phased array antenna system would require 80,000 non-RF control lines. Typically, each of these control lines must be environmentally robust, have high EMI interference immunity, and must be unobtrusive to the natural RF radiation of the phased array. In addition, a Solid State Phased Array (SSPA) is further complicated by the fact that high bias currents often dictate liquid cooling to maintain power amplifier transistor-junction temperatures at reliable levels to ensure adequate system operational lifetimes.
Accordingly, there is a need for a phased array antenna structure and method for interconnecting elements of the phased array antenna that reduces the number of electrical connections required to provide signals to multiple radiating elements and phase shifters of the phased array antenna. There is also a need for a cost effective phased array antenna architecture that has a single locus of electrical connection for RF signals and bias/control signals embedded in the multilayer linear array (or slat) interconnect substrates of the phased array antenna.